Heretofore, in an off-the-road pneumatic tire, there has been a case where a belt of a crown portion is cut because the crown portion treads on an obstacle such as a rock. During running, a crack advances into rubber of the pneumatic tire from such a cut portion as describe above, a cracked portion of the rubber is peeled off, and the pneumatic tire has thereby become junk. As a past accomplishment, by enhancing heat generation property of the rubber, the crack became difficult to advance even if the portion of the belt was cut. Accordingly, a reduction of the heat generation in tread rubber has been promoted.
For example, there is disclosed a technology for extending an entire running period of the pneumatic tire by employing tread rubber of a heat generation resistance type (for example, refer to Japanese Patent Laid-Open Publication No. 2001-213120).
However, in the tread rubber of the heat generation resistance type, in general, abrasion resistance thereof tends to be decreased. Accordingly, it has been necessary to cool the crown portion so as not to largely reduce the abrasion resistance and durability of blocks.
In this connection, in consideration for the above-described problem, it is an object of the present invention to provide a pneumatic tire which enhances the heat generation resistance of the crown portion and enhances cut separation resistance thereof.